Cancer generally refers to one of a group of more than 100 diseases caused by the uncontrolled, abnormal growth of cells that can spread to adjoining tissues or other parts of the body. Cancer cells can form a solid tumor, in which the cancer cells are massed together, or exist as dispersed cells, as in leukemia. Normal cells generally divide until maturation is attained and then only as necessary for replacement of damaged or dead cells. Cancer cells are often referred to as malignant, because they divide endlessly, eventually crowding out nearby cells and spreading to other parts of the body. The tendency of cancer cells to spread from one organ to another or from one part of the body to another distinguishes them from benign tumor cells, which overgrow but do not spread to other organs or parts of the body. Malignant cancer cells eventually metastasize and spread to other parts of the body via the bloodstream or lymphatic system, where they can multiply and form new tumors. This sort of tumor progression makes cancer a deadly disease. Although there have been great improvements in the diagnosis and treatment of cancer, many people die from cancer each year, and their deaths are typically due to metastases and cancers that are resistant to conventional therapies.
Most drug-mediated cancer therapies rely on chemotherapeutic agents (e.g., cytotoxic agents) selective for dividing cells. However, certain cancers do not respond to existing chemotherapeutic agents. Thus, there exists great need and hope, both within the medical community and among the general population, for the development of novel chemotherapeutic agents for the treatment of cancer.